Metal lock system and method

ABSTRACT

Apparatus for repairing a casting having a crack therein comprising a metal lock to extend across the crack and a lacing plug to fit in the crack, the metal lock formed as a rigid elongate member having a plurality of lobes formed from adjacent portions that are circular in cross-section and each having its center on the longitudinal axis of the elongate member, said lobes being of alternating large and small diameters and including a central large diameter lobe and at least one outer large diameter lobe at each side of the central large diameter lobe, said central large diameter lobe being spaced from each outer large diameter lobe by a small diameter lobe and with each lobe overlapping its adjacent lobe and extending through the elongate member; and the lacing plug including a head configured to receive a driving tool, a tapered shaft, a shoulder at a top of the tapered shaft, a non-threaded shaft portion interconnecting the head and the tapered shaft, a break-off groove formed in the non-threaded shaft portion adjacent to the shoulder, and straight threads formed on the tapered shaft, said threads having a uniform minor pitch diameter and a tapered major pitch diameter, said major pitch diameter being parallel to the outer diameter of the tapered shaft.

The present invention relates to cold metal repair of damaged metalparts, and more particularly, to a system for cold metal repair ofbreaks, cracks, or holes in cast iron castings.

BACKGROUND OF THE INVENTION

Many machine parts, components, brackets or supports, mountings, and thelike, are made of cast iron. Such cast iron castings have been usedbecause of the strength and durability of cast iron. However, cast ironis not infallible and sometimes such castings will become cracked orbroken. In the past, it has been very difficult, or even impossible, torepair such cast iron castings. A number of repair methods have beenutilized, each with its own advantages and disadvantages. However, noone method for repairing cast iron castings is appropriate for allrepair situations. Generally, the repair methods have included welding,brazing, epoxys, and metal stitching.

The primary drawback to using welding to repair a damaged casting isthat dependable results are not consistently obtained. Cast iron is notstructurally capable of withstanding concentrated applications of heatincident to the welding repair. A casting is frequently weakenedsignificantly or is rendered brittle in the areas of the heatapplication. So weakened, it is not unusual for a repaired casting todevelop new cracks near the welded area. Also, a casting made brittle bywelding is extremely difficult to machine and is not nearly as tolerantof stress as the original casting. Thus, welding repair of castingsusually invites recracking.

Similar disadvantages are encountered when brazing is used to repair abroken or cracked casting, because brazing also requires a specificapplication of heat to the casting and its repair area.

A further disadvantage to using welding or brazing in casting repair isthat the casting cannot normally be repaired on-site. This is becausethe complex methods of welding and brazing require specific equipmentthat may not be mobile for on-site repairs. Thus, the casting must beremoved from the location where it is used and transported to where itmay be repaired. This can be extremely expensive and frequently resultsin significant plant down-time.

Another method for casting repair is the use of epoxys or other chemicaladhesives to fill in the cracked or broken portion. However, suchrepairs are usually only temporary because the bond created will notwithstand the stresses which causes the damage to the casting in thefirst instance or the normal stresses placed on the casting duringordinary use.

Metal stitching has been used when extreme heat may alter or destroy themolecular structure of the casting, as well as when other methods areimpractical or prohibitive. With metal stitching, high tensile strengthfasteners are embedded across the cracks in the damaged casting tofirmly secure the separated elements. Then, tapered lacing plugs areworked into the metal along the cracks providing a pressure and liquidtight seal. Since most metal stitching repairs can be implementedon-site without disassembling the damaged casting, down-time and laborcosts are significantly minimized.

However, the present forms of metal stitching do have some drawbacks. Atpresent, metal stitching is performed by pounding a metal lock into aline of bores that have been prepared to receive the lock. The line ofbores run transverse to the crack. The metal lock used has a concavecurvature and usually comprises three or five lobes of equal diameteraligned such that the circle of each lobe slightly intersects the nextadjacent lobe. Because of the concave structure of the metal locks nowused for metal stitching, a couple of very significant disadvantagesoccur during the process of pounding the metal lock into position withinthe series of intersecting bores prepared to receive the lock. First, itis the outermost lobes of the metal lock which engage the prepared boresfirst. When these outermost lobes are forced into the prepared boresthey can cause the crack to further separate thereby introducing newstresses and strains to the casting. Second, this problem is furtheraggravated because as the metal lock is forced into position deep withinthe prepared bores the concave metal lock tends to flair out from itscenter thereby compounding the stresses which may cause separation ofthe crack in the casting.

One or more metal locks are usually secured within a set of preparedbores. If the length and nature of the crack require additionalconstriction, several metal locks are positioned across the crack atintervals of distance to hold the casting and prevent further cracking.When it is desired to maintain a pressure or liquid tight seal in thecasting, a series of lacing plugs are typically used to seal the crackfrom leaking. These lacing plugs are positioned in a slightlyoverlapping alignment along the length of the entire crack and betweeneach of the metal locks.

The lacing plugs presently being used are tapered plugs with taperedthreads. Such lacing plugs are placed within bores prepared along thelength and path of the crack. Because a very tight fit is desired, thethreads of the tapered lacing plugs are usually slightly oversized. Inthis manner the plug engages the threads in the bore in pressure andliquid tight engagement. After the plug is tightened into the receivingbore, the head of the plug is cut off and the remaining stub is groundand/or peened flush with the surface. The other tapered plugs arepositioned seriatim in a similar fashion along the crack. When thelacing is completed, it runs the full length of the crack and each plugintesects with the next adjacent plugs to assure that a proper seal isobtained.

The tapered lacing plugs known and used in the art have presentedseveral problems which heretofore have remained unsolved. Because thelacing plugs are tapered and have tapered threads, they are designed tothreadably engage a receiving bore which has been tapped with a taperedtap. It is the present practice to drill straight bores and then tapthat bore with a tapered tap. This is a difficult procedure thatfrequently results in damaged threads or a broken tap. When a tap breakswithin the receiving bore it is extremely difficult and time-consumingto remove the broken tap. Removal of the broken tap almost alwaysdamages the treads and damaged threads drastically increase thelikelihood that a pressure and air tight fit may not be achieved. Thus,the cost of and time loss attributable to each job requiring lacing isincreased.

Another problem with the prior art tapered plugs arises because they aretypically slightly oversized to assure a snug fit. Thus, as they arethreaded into position, they act like a wedge being driven into themetal. Consequently, with the insertion of each successive tapered pluginto the lacing, there is a tendency to loosen the prior inserted plugsand to further separate the crack. In many instances, this increases thestresses on the repaired casting and may ultimately cause furthercracking or new cracks in the casting. Also, when the plugs are loosenedtheir effectiveness is significantly reduced. Thus, after the heads ofthe tapered plugs are removed, the plugs are peened so as to seat theplugs more firmly to prevent leaking that may be caused by the loosenedplugs. Such peening damages the surface of the casting. The damagedsurface must then be repaired through time-consuming cosmetic repairtechniques.

Still another problem involves the actual threading of the plugs intothe receiving bores. If for some reason the plug binds during threading,it may break off. Such plugs do not break off cleanly above the surface;rather, they usually break off in an irregular break which is, at least,partially below the surface of the casting being repaired. Unlessrepaired by inserting another plug, a scar is left in the surface of thecasting and this scar is a weak spot in the seal.

A further disadvantage to metal stitching in general is that it has beensomewhat limited to smaller applications and applications where thestructure of the casting permits drilling at or near the area of thecrack or break. There are occasions, however, in which precisiondrilling in the area of the crack or break cannot be done. In thoseinstances, metal stitching has not been a practical approach to castingrepair.

BRIEF SUMMARY AND OBJECTS OF THE INVENTION

The metal lock device and method of the present invention eliminatesmany of the disadvantages created by the metal locks presently used formetal stitching. The metal lock device of the present inventioncomprises a substantially flat metal lock having a plurality of linearlyaligned, adjacent lobes comprising both large and small lobes. The largelobes and small lobes are arranged so as to alternate in seriesalignment and such that the circles formed by each lobe slightlyintersects with the adjacent lobe. This configuration greatly increasesthe total volume grasping area (i.e., the area defined by the linetangent to each large lobe and the outer edge of the metal lock) createdby the metal lock of the present invention. Further, the substantiallyflat nature of the metal lock enables the user to insert the metal lockinto the bores prepared by first driving the central most lobe into theappropriate bore. This tends to tie in the crack or break in the castingand significantly inhibits the flaring or separating presentlyexperienced with the concave metal locks in the prior art. Also, becausethere is no concaveness to pound out of the metal lock, there is noflairing of the lobes away from the center.

The improvement of the flat metal lock having alternate sized lobes inenhanced by the method by which the precision drilled bores are preparedto receive the metal lock. With the method of the present invention, apilot hole centered on the crack or break is drilled. This pilot holehas a diameter smaller than the diameter of the holes which will bedrilled for accepting the large lobe of the metal lock. Preferably, thediameter for each pilot hole is also slightly smaller than the holesthat will be drilled to accept the small lobes of the metal lock. Thepurpose of the pilot hole is to accept a positioning pin of a firstdrilling jig. This first drilling jig, with positioning pin in place,enables the user to precision drill another pilot hole corresponding tothe bore which will be drilled for one of the outermost lobes of themetal lock on a line substantially transverse to the crack. Once thissecond pilot hole is drilled, two pins of the first drilled jig may bepositioned within the pilot holes to assure that the next pilot hole,corresponding to the bore to receive the opposite outermost lobe of themetal lock, is aligned, positioned and drilled. If the metal lock to beused in the repair is of a threelarge-lobe configuration, theintermediate bores for receiving the small lobes of the metal bore areprecision drilled using the first jig positioned via positioning pins inthe pilot holes. These intermediate bores do not intersect with thepreviously drilled pilot holes. If the metal lock to be used in therepair is of a five-large-lobe configuration, intermediate pilot holescorresponding to the intermediate bores for receiving the large lobesare precision drilled. Then, the intermediate bores for receiving thesmall lobes of the metal lock are drilled precisely aligned via use ofpositioning pins placed in the pilot holes provided. Again, theseintermediate bores do not intersect with the previously drilled pilotholes.

After the small intermediate bores are drilled, a second drill jig isused, with positioning pins inserted into the outermost pilot holes, toprecision drill the center and/or intermediate bores for receiving thelarge lobes of the metal lock. Because the small bores do not intersectwith the pilot holes, it is much easier to start and precision drill thelarge bores than if pilot holes were not there to act as a guide. Next,a third drill jig is used with positioning pins positioned within thenewly drilled center and/or intermediate bores to precision drill theoutermost large lobes of the metal lock. When prepared in this manner,the large and small bores are precision drilled to align properly and tosnuggly receive the metal lock.

Once the bores are prepared the metal lock is placed over the preparedbores. The metal lock is inserted into the bores by hammering orpounding the centermost lobe into the centermost bore and working themetal lock out from the center to the outermost lobes. This method ofinsertion eliminates unnecessary flaring of the lock and separation ofthe crack and introduces very little or no stress to the casting in thedamaged area. This procedure is repeated for each metal lock to bepositioned across the crack or break.

After each metal lock is positioned within its respective preparedbores, stitching procedures along the crack or break are performed. Thisinvolves drilling and tapping a hole centered on the crack with isadjacent to and slightly intersecting the large central lobe of themetal lock. A plug is threaded into the tapped hole. This procedure isfollowed alternately on each side of the metal lock along the line ofthe crack or break until the entire length of the crack or break islocked into position by metal locks and a lacing of intersecting metalplugs.

The metal plugs of the present invention comprise a tapered shaft withstraight threads, a shoulder, a break-off groove, and a head. Byproviding metal plugs having tapered shafts with straight threads, thereceiving bores can be straight bores which are tapped with aconventional straight tap. Because straight taps are easier to operatethan tapered taps, and a straight tap used to tap a straight bore isless likely to break off in the bore, the use of straight taps offer asignificant savings in time and expense.

The tapered shaft enables the lacing plug to be inserted into andstarted within the straight receiving bore very easily, even if thestraight bore is positioned at an angle rather than directly vertical.Thus, the likelihood that threads will be stripped or damaged is alsosignificantly reduced with the straight-threaded tapered metal plug.

Disposed directly above the threads on the plug shaft is the shoulderwhich bites into and crushes the first few bore threads as the plug issecurely tightened. This crushing action seals the threads from pressureand liquid leaks.

Intermediate of the shoulder and the plug head is the break-off groovewhich encircles the plug shaft. This break-off groove is cut slightlydeeper than the threads on the tapered shaft. This introduces apotential break-off plane to the plug which has some definiteadvantages. By adjusting the depth of the groove in the manufacture ofthe metal plugs, it can be predetermined at what torque the plug head(which is a hex head or some other wrench or screwdriver compatiblehead) will break free of the tapered shaft. Thus, the plug head breaksoff above the surface of the casting under a predetermined torque whichwill be sufficient to permit the shoulder to crush the first few threadsof the receiving bore, but no damage other threads. This also eliminatesthe steps of cutting off the head of the plug and of peening the plug.Consequently, a considerable time-savings is introduced. Further, afterthe head breaks off, there is more room to maneuver a drill for drillingsubsequent receiving bores and the inserted plug is ready for grindingand finishing.

In instances where the casting will not permit precision drilling on thecrack or break or where a heavy duty lock is desired, a modified metallock (hereinafter called the "metal bar") is used. The metal bar is athick, substantially flat surfaced bar having a plurality of notchesalong its longitudinal sides. The notches along one side of the metalbar are offset from the notches along the other side of the metal bar.

To prepare the casting to receive the metal bar, a recess in the castingis bored out of the casting using a hogger to accommodate the dimensionsof the metal bar. Notches, corresponding to the notches in the metalbar, are carved from the walls of the recess along the outer edge of therecess hogged out from the casting. Again, the hogger or a drill is usedfor this purpose. The purpose for the notches in the metal bar and inthe walls of the recess is to receive in threaded engagement a bolt ortapered lacing plug.

Once the recess is prepared as described above, the metal bar ispositioned over the recess and inserted therein by hammering from thecenter outward. The holes defined by the notches in the metal bar and inthe walls of the recess are then tapped and filled with a threaded plug.The outer surface of the casting repair can then be peened and ground toa finshed condition, if necessary.

It is an object of the present invention to provide a significantlyimproved metal lock apparatus and method by which casting repair may beaccomplished by metal stitching.

Another object of the present invention is to provide an increased grasparea for the metal lock used in metal stitching thereby increasing thestrength of the lock used.

A further object of the present invention is to provide a method forprecision drilling of the bores which are to receive the improved metallock device.

Still another object of the present invention is to provide a metal lockdevice which does not cause stresses which tend to separate the crack orbreak in the casting.

Another object of the present invention is to provide a method for metalstitching which can be performed on-site in order to save down-time andlabor costs.

A further object of the present invention is to provide a tapered lacingplug having straight threads so as to be compatible with and easilyinserted into a straight tapped bore.

Another object of the present invention is to provide a lacing plug inwhich its head breaks off during threading at a predetermined torque,thereby eliminating the usual step of head removal.

Still another object of the present invention is to provide a lacingplug in which its head breaks off during threading at a predeterminedtorque which is sufficient to cause a shoulder for the lacing plug tobite and crush the top few threads of the receiving bore; therebyeliminating the usual step of peening the plug.

Yet another object of the present invention is to provide a metal lockdevice which can be used in instances where the casting is resistant toprecision drilling in the immediate area of the crack or break.

Other objects and advantages of the present invention will becomeapparent upon reading the following description and appending claims,and upon reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention willbecome more fully apparent from the following detailed description andappended claims taken in conjunction with the accompanying drawings.

FIG. 1 is a plan view of the top, substantially flat surface of apreferred embodiment of the metal lock of the present invention;

FIG. 2 is an elevational side view of the metal lock embodiment shown inFIG. 1;

FIG. 3 is a plan view of a partial casting surface showing a crack to berepaired and the center pilot hole;

FIG. 3A is a plan view of a partial casting surface showing three pilotholes aligned transverse to a crack to be repaired;

FIG. 3B is a plan view of partial casting surface showing five pilotholes alinged transverse to a crack to be repaired;

FIG. 3C is a plan view of a partial casting surface showing five pilotholes and four small bores disposed in transverse alignment to a crack;

FIG. 3D is a plan view of a partial casting surface showing twooutermost pilot holes and aligned intermediate thereto is the irregularcavity comprised of four small bores and three large bores;

FIG. 3E is a plan view of a partial casting surface showing a recesscomprised of alternating and overlapping large and small bores intransverse alignment to a crack being repaired;

FIG. 4 is a plan view of a partial casting surface showing a cold metalrepair of a crack using a metal lock and metal lacing;

FIG. 5 is a perspective view of a rectangular block showing a cold metalrepair of a crack using several metal locks and metal lacing;

FIG. 6 is a side elevational view of a preferred embodiment of thetapered lacing plug of the present invention showing straight threads ona tapered shaft, a break-off groove, a shoulder and a hex head;

FIG. 7 is a side elevational view of a straight bore in cut-away sectionshowing a tapered lacing plug as shown in FIG. 6 partially threadedtherein;

FIG. 8 is an enlarged side elevational, sectional view of a straightbore and tapered lacing plug showing the engagement of the threads ofthe tapered lacing plug with the threads of the straight bore;

FIG. 9 is a side elevational view of a straight bore in cut-away sectionshowing a tapered lacing plug as shown in FIG. 6 threaded therein sothat the shoulder of said plug crushes the upper few threads of saidbore;

FIG. 10 is a side elevational view of a straight bore in cut-awaysection showing a tapered lacing plug as shown in FIG. 6 after the headthereof has been broken off at the break-off groove;

FIG. 11 is a plan view of the top, substantially flat surface of apreferred embodiment of the metal bar of the present invention;

FIG. 12 is an elevational side view of the metal bar embodiment shown inFIG. 11;

FIG. 13 is a perspective view of a partial casting surface showing acrack to be repaired and the transverse recess removed from the castingto receive a metal bar;

FIG. 13A is a plan view of a partial casting surface showing a metal barpositioned within a transverse recess and defining bores (shaded) readyto receive lacing plugs; and

FIG. 13B is a plan view of a partial casting surface showing a metal barsecured in position in a transverse recess by lacing plugs.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference is now made to the drawings wherein like parts are designatedwith like numerals throughout.

FIGS. 1 and 2 illustrate a preferred embodiment of a metal lock 10 ofthe present invention. The metal lock 10 is elongated and has asubstantially planar top surface 12 which is parallel to a bottomsurface 14. The metal lock 10 also has a plurality of large lobes 16 andsmall lobes 18 which define an irregular configuration for theperipheral edge of the metal lock 10. The large lobes 16 and small lobes18 are aligned such that the centers of the circles defined thereby lieon the center longitudinal axis of the metal lock 10. In this preferredembodiment, the metal lock 10 comprises five large lobes 16 having equaldiameters and four small lobes 18 having equal diameters alignedalternately along the longitudinal axis. However, it should beunderstood that any number of large or small lobes 16, 18 may be usedand they may have various diameters. For example, for smallerapplications, a metal lock 10 with three large lobes 16 and two smalllobes 18 may be used.

It is preferred that the large lobes 16 and small lobes 18 be alignedalternately such that the circle defined by each large lobe 16intersects the circle defined by each next adjacent small lobe 18 at twopoints of intersection. This makes the irregular configuration of themetal lock 10 one of overlapping circles which is sturdy and not likelyto break. So configured, the metal lock 10 has a plurality of ribs 20which extend perpendicular to the top and bottom surfaces 12 and 14 asshown best in FIG. 2. Thus, the metal lock as shown in FIGS. 1 and 2 hasoutermost lobes 22, a center lobe 24, intermediate large lobes 26 andintermediate small lobes 28.

The purpose of the metal lock 10 is to hold a crack or break in a metalcasting closed to prevent further cracking or breaking of the casting.The metal lock 10 is inserted into a recess carved from the castingwhich has been prepared to receive one or more metal locks 10. FIGS. 3through 3E illustrate a preferred method for preparing a recess in thecasting to receive a metal lock 10.

In FIGS. 3 through 3E, the surface of a casting 30, such as a cast ironcasting or the like, is shown with a crack 32 to be repaired. Althoughcracks 32 usually extend from an edge or an appendage rather than asshown in isolated form, the teachings of this invention apply equally toalmost all types of cracks or breaks and the isolated crack shown servesadequately for illustrative purposes.

In FIG. 3, a center pilot hole 34 is drilled such that its center lieson the crack 32. It is preferred that the center pilot hole 34 have adiameter somewhat smaller than the diameter of the center lobe 24 of themetal lock to be used in the repair.

A pin for a drilling jig is positioned in the center pilot hole 34 sothat the jig can assist in drilling a second pilot hole 36 remote fromthe crack 32 and on a line substantially perpendicular to the crack 32at the center of the center pilot hole 34. This enables the repairman toprecision drill the second pilot hole 36 at a predetermined distancefrom the center pilot hole 34. That distance corresponding to thedistance between the center lobe 24 and an outermost lobe 22 of themetal lock 10 to be used in the repair. Another pin from the drillingjig is positioned in the second pilot hole 36 so that the drilling jigfacilitates the precision drilling of a third pilot hole 38 by holdingsturdy the drill at the predetermined distance corresponding to thedistance between the center lobe 24 and an outermost lobe 22 and inalignment with the centers of the previously drilled pilot holes 34 and36. FIG. 3A shows the center, second and third pilot holes 34, 36 and 38as drilled to define a line substantially perpendicular to the crack 32.Although it is preferred that the alignment of the pilot holes 34, 36and 38 be substantially perpendicular to the crack 32, it should beunderstood that such is a preferred alignment. Other nonperpendicularalignments may be used to adapt to the contour of the casting surface orto accommodate difficulties in drilling along the preferred alignment.

Intermediate pilot holes 40 are then precision drilled using a jiganchored via pins placed into one or more of the previously drilledpilot holes. These intermediate pilot holes 40 are positioned inalignment with and between the previously drilled pilot holes 34, 36 and38, as shown in FIG. 3B. The distance in which the intermediate pilotholes 40 are drilled from the center pilot hole 34 corresponds to thedistance between the center lobe 24 and the intermediate large lobes 26of the metal lock 10 to be used in the repair.

As with the center pilot hole 34, it is preferred that the second, thirdand intermediate pilot holes 36, 38 and 40 have a diameter somewhatsmaller than the diameter of the large lobes 16 of the metal lock 10. Itis the purpose of the pilot holes to facilitate precision drilling byproviding holes in which to anchor the drilling jig. Also, as will bedescribed more fully below, the pilot holes make the drilling of boresto accept the metal lock 10 easier and much more precise.

As shown in FIG. 3C, small bores 42 are drilled between the previouslydrilled pilot holes 34, 36, 38 and 40. These small bores 42 can beprecision drilled using a drilling jig which positions the drill. It ispreferred that the small bores 42 have a diameter for receiving snugglythe intermediate small lobes 28 of the metal lock 10 to be used in therepair and that the diameter of the pilot holes be such that the smallbores 42 do not intersect with the pilot holes 34, 36, 38 and 40, asshown in FIG. 3C. In this manner, the small bores 42 maintain a preciseintegrity which is ultimately advantageous to the effectiveness of themetal lock 10 to secure the casting 30 from leaking or further cracking.Also, if the small bores 42 do not intersect with the pilot holes, thepilot holes 34, 36, 38 and 40 serve more effectively as guide holes forsubsequent precision drilling.

As shown in FIG. 3D, it is preferred to next drill central bores 44 inthe casting 30 which correspond to the center and intermediate pilotholes 34 and 40. These central bores 44 can be precision drilled using ajig which is anchored into previously drilled pilot holes 36 and 38 inthe casting 30. By using pilot holes 36 and 38 for this purpose, thebores to receive the metal lock 10 are not unnecessarily damaged shouldthe jig slip or move for any reason. The central bores 44 have adiameter which will snugly receive the center and intermediate largelobes 24 and 26 of the metal lock 10 and which defines a circle whichintersects with each circle defined by the next adjacent small bore 42at two points of intersection.

An irregular recess 46 configured to receive the metal lock 10, as shownin FIG. 3E, is completed by drilling outermost bores 48 corresponding tothe second and third pilot holes 36 and 38 in which the outermost bores48 have a diameter which will snugly receive the outermost lobes 22 ofthe metal lock 10. The precision drilling of these outermost bores 48can be facilitated by using a jig anchored into position by a pin orpins in the previously drilled bores 42 and 44. It is preferred thateach of the outermost bores 48 define a circle which intersects with thecircle defined by the next adjacent small bore 42 at two points ofintersection.

As shown in FIG. 3E, the configuration of the irregular recess 46corresponds to and will receive the metal lock 10 in snug engagement. Byusing the precision drilling as described above, there is no need tochisel out between the bores as has been the case with some metal locksheretofore known in the industry. Also, as described, the irregularrecess 46 defines gripping teeth 50 which provide larger and moresubstantial grasping areas than previously used recesses for known metallocks. The depth of the irregular recess 46 depends on the thickness ofthe casting 30 and the irregular recess 46 is preferably drilled to apredetermined depth to receive one or more metal locks 10 stacked one ontop of the next.

In order to insure a snug fit while not causing the crack to furtherseparate, it is preferred that the metal lock 10 be slightly oversizedin its width and slightly undersized in its length. Sizing that hasproved to be most satisfactory is where the metal lock 10 is 0.002 of aninch wider than the irregular recess 46 and 0.008 of an inch shorterthan the irregular recess 46. This tends to pull the crack 32 togetheras the lock 10 is imbedded in the casting 30.

In order to insert a metal lock 10 into a prepared irregular recess 46,it is preferred that the metal lock 10 be placed directly over therecess 46 and then initially pounded into the recess 46 at the centerlobe 24 using a hammer or the like. This will serve to lock the crack 32and prevent further separation of the crack 32. The remainder of themetal lock 10 is then pounded into the recess 46 working from the centerlobe 24 outward towards the outermost lobes 22. If the depth of therecess 46 permits, additional metal locks 10 may be inserted in a likemanner.

For some repairs, particularly those not requiring a liquid- orair-tight seal, the lock may be complete upon peening and/or grindingthe upper metal lock 10 until it is flush with the surface of thecasting 30. If the crack 32 is large enough in length, it may beadvisable to position more than one metal lock 10 at intervals along andtransverse to the crack 32. FIG. 5 illustrates a casting repair showingthe use of several metal locks 10 positioned at intervals along thecrack which was repaired.

With regard to other repairs, a liquid- or air-tight seal may berequired. In those instances, after the metal locks 10 are set intoposition, the crack 32 should be laced with lacing plugs 52 to seal thecrack 32. The preferred method for lacing the crack 32 with lacing plugs52 is illustrated in FIG. 4. A lacing bore is drilled adjacent to ametal lock 10 so that is center lies on the crack 32 and the lacing boreslightly bites into the center lobe 24 of the positioned metal locks 10.This lacing bore is then tapped with female threads to receive inthreaded engagement a lacing plug 52 and the lacing plug 52 is threadedinto the lacing bore. The lacing plug 52 is then finished; suchfinishing may involve removing the head of the lacing plug 52 andpeening and/or grinding the portion of the lacing plug 52 remainingabove the surface of the casting 30 until the lacing plug 52 lies flushwith that surface. However, the preferred system for repairing castingsof the present invention uses an improved lacing plug which will bedescribed more fully below.

After the first lacing plug 52 is set and finished, a second lacing plugis similarly positioned, set and finished on the opposite side of thecenter lobe 24 of the metal lock 10. Subsequent lacing plugs 52 arepositioned, set and finished along the crack 32 by alternating from oneside of the metal lock 10 to the other in a similar fashion. For eachlacing plug 52 to be placed on the crack 32, a lacing bore is drilled sothat it slightly bites into the next adjacent lacing plug 52 and so thatits center lies on the crack 32. (It should be noted that the biteillustrates in FIG. 4 for each lacing plug is exaggerated for thepurposes of demonstration. It is not usually necessary to incorporatethe degree of bite shown in FIG. 4). The lacing bore is tapped forthreaded engagement with the lacing plug 52 and the lacing plug 52 isthreaded therein. The lacing plug 52 is then finished before moving onto setting and finishing the next lacing plug 52. This procedure isrepeated until the entire crack 32 is sealed from leakage. FIG. 4illustrates how the exterior of the casting repair will look afterinserting a single metal lock 10 and a plurality of lacing plugs 52along the crack. FIG. 5 illustrates how the exterior of a casting repairmay look wherein a plurality of metal locks 10 and lacing plugs 52 areused to seal the crack or break.

In the event that the lacing leaks after inserting lacing plugs 52 alongthe crack 32, additional lacing plugs 52 can be placed into the casting30 where the lacing leaks. This is done merely by locating the leak anddrilling a lacing bore at that location. The lacing bore is then tappedand a lacing plug 52 is threaded therein, set, and finished. Thisprocedure is continued until all leaks have been repaired.

Another preferred method for placement of lacing plugs 52 is to drill aseries of lacing bores at spaced intervals along the crack 32; thesespaced intervals being less than the diameter of a lacing plug 52.Lacing plugs 52 are then threaded into, set and finished for each lacingbore. A second series of lacing bores can then be drilled between andintersecting slightly with each of the lacing plugs 52 just set. Lacingplugs 52 are then threaded into, set and finished for each of the lacingbores in the second series. This method for installing lacing plugs 52along a crack is much more rapid than drilling, tapping, threading,setting and finishing each lacing bore and lacing plug 52 one at a time.

Referring now to FIGS. 6-10, it is preferred that the improved lacingplug illustrated be used in the repair system of this invention. Thepreferred lacing plug 60 has a head 62 and a tapered shaft 64 which hasstraight threads 66, a shoulder 68 and a break-off groove 70. The head62 is of a conventional configuration to facilitate the threading of thelacing plug 60 into a prepared lacing bore. It is preferred, however,that the head 62 have a hexagonal configuration so that an air wrenchcan be used to thread the lacing plug 60 into its lacing bore.

The tapered shaft 64 enables the lacing plug 60 to be inserted into alacing bore with ease and facilitates the starting of the threadedengagement with the bore. In the preferred embodiment of the repairsystem of this invention, each lacing bore 72 prepared to receive alacing plug 60 is a straight bore having straight female threads 74.(See FIGS. 7-10.) In this way, a straight thread tap may be used toprepare the bore in the conventional manner. This reduces the likelihoodthat the tap will break and eliminates the problems associated withtapping a straight hole with a tapered tap. Also, the lacing bore 72will receive the straight male threads 66 of the lacing plug 60.

The preferred lacing plug 60, as shown in FIG. 6, is shown partiallyinserted into a lacing bore 72 in FIG. 7, and an enlarged view is shownin FIG. 8. At this stage of insertion, the threads 74 are snuglyengaging the threads 66 of the lacing plug 60 and the shoulder 68 isabove the surface of the casting 30. Upon turning the lacing plug 60further into the lacing bore 72, the shoulder 68 crushes the first fewthreads 74 of the lacing bore 72, as shown in FIG. 9. This serves toseal off the lacing bore 72 from leaks and reduces or eliminates theneed to later peen the lacing plug 60.

When the lacing plug 60 is fully seated, the twisting torque applied toeat the plug 60 will cause the plug 60 to break off at the break-offgroove 70, as shown in FIG. 10. This serves to eliminate the need toremove the head by typically used conventional means. So long as thebreak-off groove 70 has a depth greater than the threads 66 and isdisposed above the threads 66, the lacing plug 60 will break above thesurface of the casting 30. By manufacturing the break-off groove 70 at apredetermined depth, the torque at which the head 62 will break off canbe determined. It is preferred that the break-off groove 70 have a depththat requires a torque sufficient to cause the shoulder 68 to crush thefirst few threads 74 of the lacing bore 72 before the head 62 breaksoff.

By using the preferred lacing plug 60, it may not be necessary to peenthe plug 60 to seat it properly. Thus, the finishing of the plug 60usually requires only grinding the shaft 64 down to the casting 30surface. This reduces the likelihood that previously inserted plugs 60will be loosened by the insertion of an adjacent plug 60 and reduces thelikelihood of leaks.

Turning now to FIGS. 11 and 12, another preferred embodiment of thepresent repair system of this invention utilizes a metal bar lock 80.The metal bar lock 80 is elongated and has a substantially planar topsurface 82 which is parallel to a bottom surface 84. The metal bar lock80 also has a plurality of notches 86 which define an irregularconfiguration for the peripheral edge of the metal bar lock 80. Thenotches 86 are aligned along the opposite longitudinal sides 88 and aresubstantially semi-circular. It is preferred that the notches 86 on onelongitudinal side 88 be offset from the notches 86 along the oppositelongitudinal side 88 (i.e., the center of the notches 86 on oppositelongitudinal sides 88 do not lie in a plane which is substantiallyperpendicular to the longitudinal axis of the metal bar lock 80). It isalso preferred that the notches 86 be aligned such that notches 86 onthe same longitudinal side 88 are disposed at equal intervals ofdistance. It is further preferred that the notches 86 on oppositelongitudinal sides 88 be offset such that the center of a notch 86 onone longitudinal side 88 lies in a plane that is one half the distancebetween the centers of adjacent notches 86 on the same side 88 from thecenter of the next adjacent notch 86 on the opposite side 88. Thispreferred configuration of the metal bar lock 80, as shown principallyin FIG. 11, introduces symmetry and strength to the metal bar lock 80which would otherwise be absent.

In using the metal bar lock 80 of the present invention in metal castingrepair, an irregular recess 90 is prepared to receive the metal bar lock80. It is preferred that the irregular recess 90 be carved or hoggedfrom the casting 30, as shown in FIG. 14, such that it conforms with theperipheral contour of the metal bar lock 80 except that where notches 86are located in the metal bar lock 80 corresponding semi-circular castingnotches 92 are provided. Such casting notches 92 to be carved out tohave substantially the same diameter as the notches 86 in the metal barlock 10.

Further, it is preferred that each of the casting notches 92 havesubstantially the same center as a corresponding notch 86 in the metalbar lock 80 when the metal bar lock 80 is inserted into the irregularrecess 90. In this manner, the notches 86 and casting notches 92 definereceiving bores 94 (shown in FIG. 13A as shaded areas) for receivingsecuring plugs 96.

The metal bar lock 80 is placed over the irregular recess 90 such thatthe notches 86 and casting notches are in register. The metal bar lock80 is then pounded into the recess 90 using a hammer or the like. It ispreferred that the metal bar lock 10 be inserted by pounding from itscenter and outwardly therefrom. Again, this procedure tends to lock thecrack 32 to prevent further separation of the crack 32. Also, similar tothe metal lock 10, one or more metal bar locks 80 can be inserted into arecess 90. Further, it is also preferred that the metal bar lock 80 beslightly oversized in width and undersized in length.

Once the metal bar lock 80 is in place, the receiving bores 94 can betapped with threads to receive securing plugs 96 to secure the metal barlock 80 within the recess 90. It is preferred that the receiving bores94 are tapped with straight threads and that the securing plugs 96 areof the preferred type of lacing plug 60 as has been described herein inreference to FIGS. 6-10.

FIG. 13B illustrates what the appearance would be of the finishedsurface of a repair using the present invention. It shows the metal barlock 80 and the securing plugs 96 disposed in the receiving bores 94 tosecure the metal bar lock 80 within the prepared irregular recess 90.

Again, the depth of the irregular recess 90 depends on the thickness ofthe casting 30 and the nature of the crack 32 to be repaired. The use ofa metal bar lock 80 to repair a casting 30 is particularly appropriatewherein, for some reason, the repairman is unable to precision drillnear the damaged area. In such cases, the repairman can still usuallyhog out by grinding a recess 90 that will receive a metal bar lock 80.

The present invention may be embodied in the specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

What is claimed and desired to be secured by United States Letters Patent is:
 1. Apparatus for repairing a casting having a crack therein, said apparatus comprisinga metal lock adapted to be inserted into a line of overlapping holes of alternating large and small diameters drilled to a desired depth and extending substantially transverse to the crack, said metal comprisinga rigid elongated member having a plurality of lobes formed from adjacent portions that are circular in cross-section and each having its center on the longitudinal axis of the elongate member, said lobes being of alternating large and small diameters and including a central large diameter lobe and at least one outer large diameter lobe at each side of the central large diameter lobe, said central large diameter lobe being spaced from each outer large diameter lobe by a small diameter lobe and with each adjacent lobe overlapping its adjacent lobes and extending through the elongate member.
 2. Apparatus as in claim 1, whereinthe rigid elongate member includes a plurality of outer large diameter lobes and a small diameter lobe interconnecting each adjacent pair of large diameter lobes.
 3. Apparatus as in claim 1, further including at least one lacing plug adapted to be inserted into said crack, said lacing plug includinga head configured to receive a driving tool; a tapered shaft; a shoulder at a top of the tapered shaft; a non-threaded shaft portion interconnecting the head and the tapered shaft; a break-off groove formed in the non-threaded shaft portion adjacent to the shoulder; and straight threads formed on the tapered shaft, said threads having a uniform minor pitch diameter and a tapered major pitch diameter, said major pitch diameter being parallel to the outer diameter of the tapered shaft.
 4. Apparatus as in claim 3, whereinthe innermost diameter of the break-off groove is smaller than the minor pitch diameter of the threads.
 5. Apparatus as in claim 4, whereinthe shoulder has an outer diameter that is larger than the major pitch diameter of the threads.
 6. Apparatus as in claim 1, whereinthe large diameter lobes each have substantially the same diameter.
 7. Apparatus as in claim 6, whereinthe small diameter lobes each have substantially the same diameter.
 8. Apparatus as in claim 1, whereinthe small diameter lobes each have substantially the same diameter.
 9. Apparatus as in claim 1, whereinat least some of the large diameter lobes are of different diameters.
 10. Apparatus as in claim 9, whereinat least some of the small diameter lobes are of different diameters.
 11. Apparatus as in claim 1, whereinat least some of the small diameter lobes are of different diameters.
 12. Apparatus for repairing a casting have a crack therein, said apparatus including at least one lacing plug adapted to be inserted into said crack, said lacing plug includinga head configured to receive a driving tool; a tapered shaft; a shoulder at a top of the tapered shaft; a non-threaded shaft portion interconnecting the head and the tapered shaft; a break-off groove formed in the non-threaded shaft portion adjacent to the shoulder; and straight threads formed on the tapered shaft, said threads having a uniform minor pitch diameter and a tapered major pitch diameter, said major pitch diameter being parallel to the outer diameter of the tapered shaft.
 13. Apparatus as in claim 12, whereinthe innermost diameter of the break-off groove is smaller than the minor pitch diameter of the threads.
 14. Apparatus as in claim 13, wherein the shoulder has an outer diameter that is larger tyhan the major pitch diameter of the threads. 